Dietary and urinary excretion of sodium and potassium associated with blood pressure control in treated hypertensive kidney transplant patients

Abstract
Background. In kidney transplant (kt) recipients , hypertension is a major risk for cardiovascular complications but also for graft failure. Blood pressure (BP) control is therefore mandatory. Office BP (OBP) remains the most frequently used for clinical decisions, however home BP (HBP) have brought a significant improvement in the BP control. Sodium is a modifiable risk factor, many studies accounted for a decrease of BP with a sodium restricted diet. Increased potassium intake has been also recommended in hypertension management. Using an agreement between office and home BP, the present study investigated the relations between the BP control in kt recipients and their urinary excretion and dietary consumption of sodium and potassium. Methods. The BP control defined by OBP <140/90 mmHg and HBP <135/85 mmHg was measured in 70 kt recipients (mean age 56 ± 11.5 years; mean graft survival 7 ± 6.6 years) treated with antihypertensive medications. OBP and HBP were measured with a validated oscillometric device (Omron M6â). 24-hour urinary sodium (Na+) and potassium (K+) excretion as well as dietary intakes (food recall) were compared between controlled and uncontrolled (in office and at home) recipients. Non parametric Wilcoxon Mann-Whitney Test was used for between groups comparisons and Fisher’s exact test for frequencies comparisons. Results. Using an agreement between OBP and HBP, we identified controlled (21%) and uncontrolled recipients (49%). Major confounding effects susceptible to interfere with the BP regulation did not differ between groups, the amounts of sodium excretion were similar (154 ± 93 vs 162 ± 88 mmol/24h) but uncontrolled patients excreted less potassium (68 ± 14 vs 54 ± 20 mmol/24h; P=0.029) and had significantly lower intakes (3279 ± 753 vs 2208 ± 720 mg/24h; P=0.009), resulting in a higher Na+/K+ ratio. Systolic HBP was inversely and significantly correlated to urinary potassium when age, BMI and urinary sodium were controlled (r= -0.46; P=0.002). When age, BMI and urinary potassium were controlled, a positive relation was observed with urinary sodium (P=0.042).
Conclusions. Half of the treated hypertensive kt recipients remained uncontrolled in office and at home. Restoring a well-balanced sodium/potassium ratio intakes could be a non pharmacological opportunity to improve blood pressure control.